Hard disk drives are common information storage devices. Referring to FIG. 1a, a conventional disk drive 100 essentially consists of a series of rotatable disks 101 mounted on a spindle, and a Head Stack Assembly (HSA) 130 which is rotatable about an actuator arm axis 102 for accessing data tracks on disks during seeking. The HSA 130 includes at least one arm 104 and HGA 150.
Referring to FIG. 1b, the HGA 150 includes a slider 103 having a reading/writing transducer imbedded therein, a suspension 190 to load or suspend the slider 103 thereon. As illustrated, the suspension 190 includes a load beam 106, a base plate 108, a hinge 107 and a flexure 105, all of which are assembled together.
FIG. 1c shows a more detailed structure of the flexure 105. As illustrated in the figure, a plurality of suspension traces 120 is formed on the flexure 105 along length direction thereof. One end of the suspension traces 120 is electrically connected to a preamplifier (not shown), and the other end thereof extends into a suspension tongue 136. Concretely, the suspension tongues 136 locates at the leading portion of the flexure 105, which adapts for supporting the slider 103 directly. The flexure 105 further includes a pair of struts 121 extending from two lateral sides of the suspension tongue 136, so as to support the suspension tongue 136 at the center section thereof. The leading end of the suspension tongue 136 is partially supported by a pair of protrusions 122, and the tailing end of the suspension tongue 136 configures a limiter 123 for stably holding the slider 103.
As shown in FIG. 1d-1e, the flexure 105 is a laminated structure which includes a stainless steel layer 141 and a polyimide layer 142 formed thereon and a cover layer (not shown). The suspension traces 120 are formed on the polyimide layer 142 at the top surface thereof, which are covered by the cover layer. Commonly, the cover layer is made of copper, so as to protect the suspension traces 120. A plurality of bonding pads 124 are formed on the polyimide layer 142 at the bottom surface thereof at the leading end of the suspension tongue 136, which connect with the suspension trace 120 and bond with the leading edge of the slider 103 for electrical connection. Commonly, the bonding pads 124 of the suspension tongue 136 and the slider 103 are securely fixed by a solder ball bonded therebetween. As a result, a high temperature is utilized while bonding the solder ball. Thus, the temperature of the bonding pad 124 is quite high so that the polyimide layer 142 may be damaged potentially. Basing on this case, at the direct backside of the bonding pads 124, a supporting piece 125 made of stainless steel is formed on the polyimide layer 142 at the bottom surface, which supports the bonding pads 124 rearwards. As a result, the supporting piece 125 protects the suspension tongue 136 under the thermal bonding condition with a high temperature.
In a common disk drive unit, the slider flies only approximately a few micro-inches above the surface of the rotating disk. Generally, the flying height of the slider is considered as one of the most critical parameters affecting the disk reading and writing performances. More concretely, a relatively small flying height allows the transducer imbedded in the slider to achieve a greater read/writing resolution between different data bit locations on the disk surface, thus improving data storage capacity of the disk. Thus, it is desired that the slider has a small flying height to achieve a higher data storage capacity.
Meanwhile, it is strongly expected that the flying height be kept constant all the time regardless of variable flying conditions, since great variation of flying height will deteriorate reading/writing performance of the slider. However, the stability of the flying slider is hard to control and maintain, since it is easy to be effected by the external environment, such as temperature, stress, impact and the like.
However, with the mentioned-above design of the supporting piece 125, the whole supporting piece 125 behind the bonding pads 124 limits the stress releasing which is generated by bonding the slider 103 with the bonding pads 124. As a result, stress is gathered on the suspension tongue 136, then will trigger the slider 103 formed thereon. Thus, the flying height of the slider 103 is very unstable, which deteriorates reading/writing performance of the slider 103.
Another important index of the slider is thermal crown change. As shown in FIG. 1f-1g, at the room temperature, a little crown change A generates on the slider, and a great crown change B generates at 55 degree. That's because the bonding pads 124 between the slider 103 and the suspension tongue 136 will expand under the high temperature condition, and the stress generated fails to be released, which causes the slider to generate the great crown change. And the crown change of slider varies with the temperature variation which tremendously affects the flying characteristic of the slider, and impacts the reading and writing ability of the slider in turn, finally impacts the dynamic reliability performance of the disk drive unit.
Furthermore, the thinner slider will aggravate the thermal crown change. The types of slider used recently include the conventional thicker Pico slider (length=1.25 mm, width=1.00 mm, height=0.3 mm), Pemto slider (length=1.235 mm, width=0.7 mm, height=0.23 mm), U-Pemto slider (length=1.235 mm, width=0.7 mm, height=0.18 mm) and Femto slider (length=0.85 mm, width=0.7 mm, height=0.23 mm) which have much thinner size. Nowadays, the thinner slider with smaller cubage is popular and becomes the main trend, however, some drawbacks generate at the same time. For example, when the thinner slider, such as the U-Pemto and Femto sliders are mounted on the suspension tongue, flying height thereof is much hard to control and very unstable under the unstable external environment. And the thermal crown change of the thinner slider is much greater under the thermal condition. As a result, the reading and writing ability of the slider is weakened and, in turn, the dynamic reliability performance of the disk drive unit is reduced.
Thus, there is a need for an improved suspension adapted for the thinner slider, which can release the stress generated between a slider and the bonding pad of the suspension, reduce the temperature impact to the suspension, and reduce thermal crown change of the slider mounted thereon.